Television apparatus



Jan 2, 1940. H. R. LUBCKE I 2,185,640

TELEVISION APPARATUS Filed March 25, 1938 I Inventor; T f8.

34 .zg. ry Lube/w,

Patented Jan. 2, 1940 UNITED STATES PATENT OFFICE TELEVISION APPARATUSApplication March 23, 1938, Serial No. 197,637

11 Claims. (01. 1-78'7.1')

My invention relates to the art of television, and particularly tomethods and means for scanning motion picture films by the use ofmechanical equipment.

It is well known that practical limitations, as to smallness andaccuracy of placement of the holes in scanning disks, seldom allowentirely satisfactory results where disk scanning is used for highdefinition television, as when images of 300 to 441 lines are desirable.The principal object of the present invention, therefore, is to provide.a simple optical system for avoiding the effect of such limitations intelevision reproduction.

Subsidiary objects, all of which contribute to the attainment of saidprincipal object, include; first, provision of much smaller effectiveoptical apertures in disk scanning than are attainable by the use ofphysical apertures in the ordinary manner; second, to provide means foradjusting the size of such optical apertures over a wide range, withoutchanging the physicalapertures; third, to make it feasible to employ aset of physical apertures, for, securing small eifective opticalapertures for image scanning, coincidently with much larger effectiveapertures for generating synchronizing pulses; and, fourth, to devise apractical method for initiating a synchronizing.

pulse immediately preceding each. image scan, said pulses occurringalways at a definitely fixed time interval before the image scan begins.

My objects have been attained in the manner illustrated in theaccompanying drawing, in which- Figure 1 is a much enlarged fragmentarycrossse'ction of an ordinary scanning disk, in thep'lan'e of the axis ofa typical scanning aperture therethrough;

Figure 2 is a view of the righthand face of said disk fragment, whenlooking in the direction of angle a from the perpendicular;

'Figure 3 is a diagrammatic illustration of the complete optical systemof the present invention in elevation;

Figure 4 is a diagrammatic illustration of said system in plan;

Figure 5 is a fragmentary'face view of a scanning disk which is faultyby reason of unequally spaced scanning apertures, in aid of thediscussion to follow regarding the efiect of such spac- Figure 6 is alarge scale diagrammatic illustration of a portion of the screen of acathode ray tube, while it is reproducing a television image initiallyscanned by a disk having the faults ex- I hibited by Fig. 5;the'reproduction being synchronized by pulses occurring at equal timeintervals; and

Figure 7 is a similar diagrammatic illustration of said screen while itis reproducing an image initially. scanned by said faulty disk, but withthe reproduction synchronized by pulses produced by the same aperturesthat were used in the. initial" image scanning.

Certain of the illustrated proportions have been considerablyexaggerated, for convenience in this disclosure. Similar referencecharacters refer to similar things throughout the severalfigures of thedrawing.

The body of a mechanical scanning disk is. shown at 8 in the drawing,both pictorially and diagrammatically. The disk is assumed to berotatable about its axis 9, in the direction of arrow H. Such a diskalways is provided with a large number of spaced" cylindrical scanningapertures therethrough, of which three are indicated in Fig. 5 at I2, l3and M- respectively.

Figure 1- shows a relatively thick scanning disk fragment, on a greatlyenlarged scale, with sucha. scanning aperture therethrough. The workingportion of this aperture is cylindrical, as'at l5; and we will assumethat its cross-sectional area is correctly represented by A, itsdiameter by D, and its axial length by T. In cases like this,countersinkingv of the scanning holes is required, as at it, to secureholes of the desired length. If the disk were made of thickness T at thescanning holes, no such. countersinking would be required, of course;but, as a practical matter, such. a disk would be too thin, and thus besubject to, mechanical distortion. Countersinking the holes overcomesthis difficulty, the shape of the countersinking being immaterial solong as it entails no obstruction to rays emerging from the cylindricalportion of the apertures.

Such physical apertures afford the possibility of using greatlydecreased optical apertures; by properly proportioning their axiallengths and diameters, and by causing light to impinge thereon at anadvantageous angle from the perpendicular, which angle will herein bedesignated as on. 45 It should be remembered, however, that the usefullight transmitted through disk apertures must come from only oneelemental area of the scene being scanned at every instant. Light whichis reflected from the walls of the apertures does not. 5 meetthisrequirement, and must not be permitted to reach the means employedfor television transmission. All of this will be explained more fullybelow.

In the use of a preferred embodiment of the dicular, and the front faceof the disk, at the zone of the scanning holes, thus becomes floodedwith image modulated light.

By referring now to Fig. 1 it will be seen that only light within thebeam dd' can pass directly through the scanning hole. The crosssectionof this beam is the same as the overlapping portions of the projectedareas of. the two ends of aperture l5 when seen in the direction of thebeam, and hence is represented by the small area a of Fig. 2. Otherlight entering aperture i5 will be reflected from the wall thereof, inthe manner indicated by the beam r-r'.

Of all the possible values of numerics D, T and or, the optimum resultsare obtained when T=2D and a=22 Figs. 1, 2 and 3 have been drawn to thiscriterion. This relation does not allow of multiple reflection withinaperture l5; and the cross-section of the efiective image aperture,represented by numeric a; is the smallest obtainable with the givenphysical aperture and angle of incidence. The angle between direct raydd' and the reflected portion of r--r', is 45 under such conditions.

It is important to prevent multiple reflection from the wall of apertureHi to the greatest possible extent, because any reflected light whichshould leave the aperture in a direction near enough to that of thedirect beam to impinge on image transmission devices, would causeproportional blurring of the received image. This is for the reason thatthe reflected rays necessarily originate at different parts of the imagefrom the source of the direct rays; and the reflected rays cannot bewholly eliminated by blackening or otherwise treating the interiorsurface of aperture I5. Almost any surface will reflect considerablelight at the small reflection angles occurring in such apparatus as weare considering It is desirable that the effective image aperture bemade as small as possible, to permit of securing greater definition inthe transmitted image; but the use of relatively large physicalapertures increases the precision with which the scanning disk can bemade. Although the smallest practical drill should be used for the diskapertures, so that the overall dimensions of the equipment may be keptwithin reasonable limits; the accuracy with which small holes may bepositioned, and their size be maintained invariable, decreases with thesize of the drill used. By employing my method of using a scanning beamwhich is oblique to the axes of the scanning apertures, it is possibleto obtain an effective image aperture having a cross-section area whichis but a small fraction of that of the smallest physical aperture thatis attainable. It is entirely feasible to secure, in this manner, aratio between cross-sectional areas of the order of 1 to 25.

It is desirable that the angle between the direct and reflected lightbeams be great, as of the order of 45, to enable the image transmittingmeans to be positioned so as not to intercept reflected rays.

Itis easily possible to vary the relation between the cross-sections ofthe effective and physical apertures, a and A respectively, by changingeither the angle of incidence or, or the length T of the physicalaperture. Effective aperture size and shape may thus be adjusted bymerely tilting the base of the projecting apparatus, and no structuralchanges are required.

It will be noted that the major axis of area a is parallel to thedirection of scanning, and that this area possesses a very desirableshape for a scanning spot. Spurious patterns do not occur so readily inthe reproduced field of view, when such a spot is used, as whenrectangular scanning apertures are employed.

The emergent image scanning beam d d' is focused upon a photoelectricdevice 2 i, by means of a lens 22, for actuating the image transmissionapparatus.

In Figs. 3 and 4., means for producing thenecessary high frequency (orline) synchronizing pulses are diagrammatically illustrated. For suchsynchronization I focus light from a source 23 perpendicularly upon thesurface of' isk 8, by means of a lens 24, and allow the beam to passthrough the scanning apertures parallel to the axes thereof, I thusutilize the entire crosssection of the apertures for producing thesynchronizing pulses. The duration of the latter is two or three timesas long as the time required for scanning one elemental area of theimage field of View, which is desirable. The optical efficiency of thispulse producing means is many times larger than it would be if only theeffective image aperture (of cross-section a) were utilized. A watt lampmay be used at 23, and an image of its filament is focused upon thesurface of disk 8 in the aperture zone, by means of lens 2%. Lens 25concentrates the light emerging from the apertures upon a photoelectricdevice 26, for initiating the high frequency synchronizing pulses. mentimage on the disk, in a tangential direction, by employing a wideractual filament, the duration of the high frequency synchronizing pulsemay efficiently be made as long as reasonably desirable. Elements 23,24, 25 and 26 are in alignment as indicated by the line p-p', and thelatter coincides with the axes of the physical apertures at their uppercentral positions.

The advantage of having a pulse aperture materially larger than theeifective image aperture, will be appreciated by those familiar with theart, in view'of what has been said.

Means for producing the low frequency. synchronizing pulses, and thecharacter of the amplifiers, radio transmitter, receiver, cathode raytube, and of the scanning devices required to complete the televisionsystem, are fully illustrated and described in my U. S. Patent No.2,055,748, issued September 29, 1936. They form no part of the presentinvention, and need not be further considered herein.

According to the present invention, it is necessary to have only onering of apertures in disk'B; and this single set of apertures maybeutilized both for image scanning and high frequency pulse production, inthe manner described. Such uti-' lization makes it impossible for timedisplace ments to occur as between scanning and pulse production. Nodependence upon precision of construction and mechanical skill isnecessary;

By increasing the width-of the filaand, at the same time, the highestdefinition re- 7'5 I curately placed scanning apertures atpresent requirements be satisfactory television are attainable;

By referring to-Fig-.- 4; it will be noted that,

sequentially; the' pulse optical system (represented by elements23 to25) is located beforethe image optical system- (represented by elements-I 'l to Z l) As each and every disk aperture functions, it first servesto initiate a synchronizing pulse, and immediately-thereafter to scan aline across the image. The time interval between these two functions isnecessarily fixed and constant, by

reason of the constantspeed of the scanning disk.

Inaccuracies in spacingthe diskhcles therefore are of no particularconsequence.

Fig. 5" shows aportion of a scanning disk having three inaccuratelyspaced apertures l2, l3 and- M therethrough'; and a simple opticalimage, comprising bars 21 and 28 of different width, is represented-asbeing focused upon the face of the disk The inaccuracy of spacing thescanning apertures has been exaggerated, for convenienceof"illustration. As the disk revolves in'the direction of arrow l I,aperture Hlwill scan bar 2'! first; and then bar 28. Such a scan isdiagram.-

matically-shown as reproduced on the receivingscreen, in'Fig. 6 at 29,

Now if disk. scanning aperture it is positioned to the leftof-its"proper location 3!, its scanning will'occur later than it should, andordinarily it would appear onthe receiving screen as at til in'Fig;--'6.If scanning aperture I2 is positioned too far to the right of its properlocation 33, its scanning-will occur too soon, and ordinarily itwouldappear on the receiving screen as at in Fig. 6.-

s Fig. 6 thus illustrates the serious type of distortion-which occurs inreceived television images when the synchronization is by pulses whichare equally spaced intime. Such distortion is espercially noticeable'inthe case of vertical edges of buildings, and mother places where finedetail is carried over several horizontal scans. Inacsult ininaccurately timed synchronizing pulses,

and these are in random relation to the image scanning inaccuracies.Since the algebraicsum 011311859 errors must be considered, it ispossible that certain of them will be reduced in effect, or

even eliminated; but, in general, the result is worse than indicated inFig.i6.

In thesystem of the present invention, a synchronizing pulse alwaysprecedes each scan, by exactlyv the same time interval; and thereproducedimage will'be entirely free of distortions ;due toinaccuracies in placingthe disk scanning apertures. The factthat onescan" at the receiver maybe initiated at a slightly different time, orthat it may be'of slightlydifferent duration, than normal or average, isof no practical consequence.

Oscillators which are adapted for television scanning, must'be sensitiveto synchronization to such aniextent as readily to follow the slightirregularities of timing that may be due to ordinary faulty spacing ofthe disk scanning apertures. 3Non-oscillating receiver scanning sources,which {the methods of the present invention, appear in relation 1 totheir respective scans'and to each other." The receiver is brought intostep, and made ready for scann-ipgf upon the arrival of each-synchronizing-=pulse. Then, after a short but definitely fixed andconstant time interval,

fieldof view, in synchronism with the transmitter scanning. Thus theleft margin of the received scene is developed as a straight verticalline. The velocity of the scanning disk at the transmitter is constant,by reason of its inertia. Consequently, because of the concurrence ofthese influenceseach element of the field of view at the receiver isaccurately placed with respect to corresponding elements of the scans,both above and below; as shown at 2i and 28 in Fig. '7. It cannot beotherwise, and there is no possibility of maladjustment aifectingthisresult.

The only effect that inaccurate placement of the disk apertures canhaveupon the received image, is to make the scans of different length, asshown at 35, 36 and 3] of Fig. '7. This will happen because, when suchinaccuracies exist,

its scanning starts at the'left-hand side of'- the succeedingsynchronizing pulses will occur too soon or too late for uniformity.This result, however, can affect detail only at the extreme right handmargin of the scene; and, for nearly every practical purpose, it isentirely negligible.

Attention is particularly directed to the fact that mutual inclinationof the axes of the pulse and image systems practically eliminatesadverse effects of aberration, reflection, and random light in general.Suchinclination, moreover, affords spacefor placing the optical elementsto the best advantage. The lenses may be located close to the focalplane on the scanning disk; and no other retracting, or any reflecting,elements are re quired. Hence great simplicity, coupled with highefiiciency, is attained. I

The figures of the appended drawing illustrate disk scanning apparatuswherein the scanning apertures are drilled perpendicularly to'thesurfaceof the disk; and the use ofan image optical system which isinclined downwardly from a light source to a photoelectric device, at anangle of 22 /2, Certain other arrangements are feasible, withoutdeparting from the essence of the present invention. Among suchvariantsare: I First, the inclination of the image optical system may bereversed, the path from the light source to the'photoelectric devicebeing inclined upwardly instead of downwardly, at an angle of 2 /5;

Second, the scanning apertures may be drilled at an angleof 22 withrespect to the axis of the disk, either in a convergent or divergentdirection. In this case the image light'beam. d-d must be parallel tothe axis of the disk, instead of beinginclined thereto; and the pulseoptical system must be inclined in the same way, and to the same degree,as the scanning apertures;

Third, the axes of the scanning apertures may be oblique to radialplanes containing the axis of the disk, as well as to "the axis of thedisk alone.

In-such a case, if the latter obliquity is 45, the cross-section a ofthe image beam 0Z-d' willhave its major axis at an angle of 45 withrespect to the direction of scanning. Such positioning of the scanningspot Willgive greater resolution along each scanning line, but lessbetween adjacent'scans, than the originally described arrangement.Moreover, the angular separation between the direct and reflected raysof the image light will be 22 /2", instead of 45; and

Finally, it will be understood that the teachings of this disclosure maybe applied to other equipment-known to the television art. For instance,the well known type ofscanning disk, having one or more spirals ofapertures; may takethe place of disk 8 described herein. In this case 75cross-section.

the apertures aredrilled at an angle to-the axis of the disk, asoutlined in the second variant above, and a synchronizing beam isprovided having a radially long, and tangentially narrow, This beam ismade to impinge upon the surface of the disk from a point within theinner limit of the aperture spiral, to a point without the outer limitof said spiral. Each aperture thus would be adapted to produce asynchronizing pulse as it passes said beam.

Having thus fully disclosed my invention, I claim:

1. Television apparatus comprising; a rotat-' able scanning diskprovided with cylindrical apertures therethrough, the axial length ofthe apertures being greater than the diameter; and means for projectingradiant energy through each of said apertures in turn, at an angle toits axis, for securing direct energy beams of small {cross-sectionrelative to said apertures, while diverting the balance of said energyby reflection from the interior of said apertures at a substantial angleto said direct energy beams.

2. Television apparatus comprising; a rotata- -ble scanning diskprovided with cylindrical apertures therethrough, the axial length ofthe apertures being greater than the diameter; means for projectingimage-modulated light through each of said apertures in turn, at anangle to its axis; and a photoelectric device positioned to receive onlythat portion of said light which passes directly through the apertures,the remainder of said light being reflected from the interior of saidapertures and leaving at a substantial angle to said direct light.

3. Television apparatus comprising; a rotatable scanning disk providedwith cylindrical apertures therethrough, the axial length of theapertures being twice the diameter thereof; means for projectingimage-modulated light through each of said apertures in turn, at anangle of 22 to its axis; and a photoelectric device positioned toreceive only, that portion of said light which passes directly throughthe apertures when so projected.

4. Television apparatus comprising; a rotatable scanning disk providedwith cylindrical apertures therethrough, the axial length of theapertures being greater than the diameter; each aperture axis beinginclined 22 tothe axis of the disk in a plane which includes both saidaxes, and also being inclined not more than to said plane.

5. Television apparatus comprising; a rotatable scanning disk providedwith cylindrical apertures therethrough, the axial length of theapertures being greater than the diameter; means for projectingimage-modulated light through each of said apertures in turn, at anangle to its axis; a photoelectric device positioned to receive onlythat portion of said light which passes directly through the apertures;means for projecting unmodulated light for synchronization through eachof said apertures in turn, in a direction parallel to its axis; and asecond photoelectric device positioned to receive said unmodulatedlight.

6. Television apparatus comprising; a movable scanning member providedwith apertures therethrough, the axial length of the apertures beinggreater than the diameter; means for projecting image-modulated lightthrough each of said apertures in turn, at a substantial angle to theaxes thereof; photoelectric means for intercepting only-said light whichpasses directly through said apertures; and means for projecting light.

for synchronization through each of said apertures in turn, in adirection substantially parallel tical system being inclined at thegreater anglethereto.

8. Television apparatus comprising; a rotatable scanning member providedwith apertures therethrough; an image optical system inclined to theaxes of said apertures when at their operating positions; and asynchronizing pulse optical system coaxial with said aperture axes. atsaid positions; the pulse system being positioned adjacent to the imagesystem and so' that each aperture will coact first with the pulse systemand then with the image system, thereby producing a synchronizing pulsethe same interval before image scanning begins for each aperture.

9. Television apparatus comprising; a movable scanning member providedwith cylindrical apertures therethrough, the. axial length of the.

through each of said apertures in turn, at an angle to its axis, forsecuring direct light beams of small cross-section relative to saidapertures,"

while diverting the balance of said light by fiection from the interiorof said apertures to secure effective optical apertures which aresmaller than the physical apertures; the relative sizes of said twokinds of apertures being deing the angle.

10. Television apparatus comprising; a rotatable scanning memberprovided with cylindrical I pendent upon said angle, and adjustable byvary- I apertures therethrough, the axial length of the apertures beinggreater than the diameter; and

means for projecting image-modulated light through each of saidapertures in turn, at an angle to its axis, for securing direct lightbeams of small cross-section relative to said apertures, while divertingthe balance of said light by reflection from the interior of saidapertures to secure effective optical apertures which are smaller thanthe'physical apertures; the relative shape of said two kinds of.apertures being dependent upon said angle, and adjustable by varyaplane, said image having an area greater than the area of one saidmovable aperture, at a position traversed by said apertures.

HARRYR. LUBCKE.

